(1) Field of the Invention
The present invention relates to novel magenta dye-forming couplers (hereinafter referred to as magenta couplers), and in particular, to magenta couplers that improve the sensitivity, the color density, and the gradation (.gamma.) of the image of silver halide color photographic materials. More particularly, the present invention relates to 1H-pyrazolo[1,5-b]-1,2,4-triazole magenta couplers or 1H-pyrazolo[5,1-c]-1,2,4-triazole magenta couplers being characterized by having at the 6-position a phenoxy group, on the ortho-position of which is an alkoxy group or an aryloxy group.
(2) Description of the Prior Art
It is well known that aromatic primary amine-type color developing agents, which have been oxidized by an exposed silver halide that acts as an oxidizing agent, and couplers react to produce indophenols, indoanilines, indamines, azomethines, phenoxazines, phenazines, or dyes similar thereto, to form images.
Of these, 5-pyrazolone, cyanoacetophenone, indazolone, pyrazolobenzimidazole, and pyrazolotriazole-type couplers are used to form magenta color images.
Hitherto, most magenta color image-forming couplers that were widely used in practice and studied were 5-pyrazolones. However, it was known that the dyes formed from 5-pyrazolone-type couplers had undesired absorption of yellow components at around 430 nm, which caused color turbidity.
As magenta color image-forming compound skeletons are suggested pyrazolobenzimidazole skeletons described in British Patent No. 1,047,612, indazolone skeletons described in U.S. Pat. No. 3,770,447, and pyrazolo [5,1-c]-1,2,4-triazole skeletons described in U.S. Pat. No. 3,725,067.
However, the magenta couplers described in these patents are still unsatisfactory in that when the magenta coupler is dispersed in a hydrophilic protective colloid, such as gelatin, and mixed with a silver halide emulsion, only an unsatisfactory color image occurs, or in that the solubility into a high-boiling organic solvent is low, or the synthesis is difficult, or the coupling activity is relatively low when a common developing solution is used, or the light-fastness of the dye is quite low.
The inventor of the present invention studied various new types of magenta color image couplers that exhibit no subsidiary absorption at around 430 nm, which is the most disadvantageous point of 5-pyrazolone-type couplers in view of the hue, and found 1H-pyrazolo[1,5-b]-1,2,4-triazole magenta couplers that exhibit no subsidiary absorption on the short wavelength side, are high in fastness of the dye image, are easy to synthesize, and are disclosed in Japanese Patent Application (OPI) No. 171956/1984 and U.S. Pat. No. 4,540,654. These couplers are excellent in color reproducibility, synthetically excellent, and they have characteristics that when a coupling split-off group is introduced to the coupling-active position they can be made two-equivalent, and the amount of silver used can be reduced. However, when the coupling split-off group designated by (X) in the coupler is halogen, alkylthio, or arylthio, which can be easily synthesized, the magenta couplers have the problem that the sensitivity and the gradation (.gamma.) of a photographic material obtained thereof are a little inferior to those of 5-pyrazolone type magenta couplers. Therefore, couplers wherein X is an aryloxy group as disclosed in Japanese Patent Application No. 176352/1984 were found as one means of solving the problem. However, although the aryloxy coupling-split-off, type couplers could solve the above problem, they have defects including low synthesis yield, so that they are not adapted to large-scale synthesis, and the stability is low. Pyrazolotriazoles described in U.S. Pat. No. 3,725,067 mentioned above also have similar defects.